I'm scratching my head trying to figure this one out. Here's the story: I started brewing extracts, and they all came out great. I wanted to get into all-grain so a last year I ordered myself the supplies and have been trying to make a single good all-grain batch since then.

I am using the brew-in-a-bag method, and use pilsner malt, crystal malts, special b, flaked wheat, flaked oats, etc. Every beer, from the lightest pale ale (pils, crystal 40L, lots of hops) to darker beers (pils, special b) has come out with a weird flavor that I can only describe as "dark" and maybe burnt tasting, very bitter, not pleasant at all. Roasted malts used in stouts taste significantly better than this. The lightest beers, like a wit, taste dark and undrinkable. It kind of makes you pucker, but I can't really tell if it's astringent or sour or something else.

I've been doing one to three gallon batches. I strike at 165-170F or so, mash at 155F for an hour with a mash PH of around 5.0 according to my PH test strips. I'm using tap water, which I see others online say is okay (Seattle area). I've been mashing in my bottling bucket so that I can let a lot of the gunk settle out and use the spigot to pour into my pot for the boil, leaving behind most of the finer sediment that would otherwise be on the bottom of the pot with brew-in-a-bag. I boil for an hour with multiple hop additions based on the recipe, then cool in a bath of ice water, aerate by vigorously stirring and then pitch. The yeast always take off within a few hours and the fermentation goes great. Tasting the beer during bottling it tastes okay (I tend to try after the priming sugar is added, so it may mask the flavor), but by the time I drink the beer in a week or two it has this off flavor. I've tried letting the beer sit for a couple of months, but the flavor just stays and stays. I've tried both letting it sit in primary for a month and bottling after a week to let it sit in bottles for a month or two.

I'm really at a loss here and getting incredibly frustrated. Any suggestions would be really nice. I wish I knew what I was doing wrong. Feel free to try and help me put my finger on the exact terminology to use for this off flavor - I'm not all that experienced at describing them.

Edit: thought I would add that I don't have a grain mill. I have bought both pre-crushed and whole grains. Until I get a mill I've been using the blender, doing one cup at a time for 5-8 seconds on low to expose the kernels. Both the blender-chopped malt and the pre-crushed malt from a homebrew shop exhibit the off-flavor problem, so I can't imagine it's the crush.

  • 1
    a well-written question. Are you applying any heat to maintain the mash temperature, and if so, what kind.
    – mdma
    Jun 17, 2012 at 23:19
  • 3
    If the beer tastes good when you're bottling, and then tastes bad after a week or two in bottles, there must be something going on in the bottles. How are you priming the bottles? If you're not doing anything outrageous with respect to priming sugars, etc., then I would probably conclude that some micro-organism, is affecting the flavour of the beer post bottling. That being said, I can't think of any infectious agent that produces "burnt" or "dark" flavours. Jun 18, 2012 at 1:33
  • I do not apply any heat during mashing, just wrap in a blanket and lose about 5F over the course of an hour. I can't taste it before bottling, but most of the time I make the mistake of not tasting until after adding the priming sugar. My thought is that the sugar is masking the taste, or I'm just not paying attention. I just can't imagine it's an infection - I've had infections before and burnt is not how I'd describe them, more like sour / funky / moldy instead. Also, I'm priming with plain white table sugar, boiled in a bit of water to sanitize.
    – Daniel
    Jun 18, 2012 at 2:01
  • 1
    Are you filtering your tap water?
    – baka
    Jun 18, 2012 at 11:16
  • I am not filtering my water. Not sure if I should be.
    – Daniel
    Jun 18, 2012 at 22:05

6 Answers 6


This screams out "mash water problem" to me. Anytime you go from good extract beers, to "bitter/astringent/chalky/burnt" flavors in all grain, you can bet your buns that its a mash water pH problem. Also, a mash pH of 5 sounds really low to me. I shoot for 5.5 on average.

Water chemistry for all-grain is honestly the most "sciency" part of home brewing, and can be down right intimidating. I've had a few beers turn out exactly like what you are describing and here's what I did to improve my process:

1) Stop using tap water. There's no sense fighting this battle right now. Use all Reverse Osmosis water. This is water that's very close to distilled in terms of purity, and can be bought at my supermarket for $0.30 per gallon, making the cost negligible. You can make every style of beer in the world by starting with RO and then building up your mineral profile to match the style.

Once you get 20-30 all grain batches down without this same problem, then you can investigate using your tap water again, but it will be much more complicated. No point fooling with that now.

2) Download and use the "EZ Water Spreadsheet". Its an excellent tool for calculating your mash pH and mineral content of the final beer. You plug in your base water (easy because its all RO), your grains, and the minerals you are going to add, and the spreadsheet tells you your mash pH.

Regarding minerals, I'm not sure how much you know, but here's a high-level overview: Every beer needs at least trace elements of Magnesium, Sodium, Calcium, Chloride and Gypsum (So4). Some styles of beer, like Pilsner, have very little mineral content at all. Some, like Irish stouts, have very high levels of minerals. Adding calcium chloride or Gypsum brings down your mash pH, as does dark roasted grains, and acid malt. If you add too much dark roasted grain, you need to either cut out some of your acidifying minerals, or start with alkaline water. The more Calcium Chloride you add to the beer, the more malty and "round" it tastes, while Gypsum creates a sharper hop flavor that can bleed over into kinda dry flavor if you add too much.

For a given style, I first google "[STYLE] basic water profile" and then I find what most brewers are using for minerals. It will be expressed something like this jibberish: "Ca 94, Mg 15, Na 18, Cl 80, SO4 130 - ratio 0.60" That tells you the parts per million (or "PPM") concentrations of those minerals in the final beer (not necessarily the mash). From there, I add my grains to the spreadsheet, add my mash and sparge volumes, and then add 2grams each of Calcium Chloride and Gypsum under their areas. I also start with 2ounces of acid malt as well. From there, I adjust as needed. For example, if I have too much mineral content (the row at the bottom shows you the final minerals), then I take away from CalChlor and Gypsum. As I take them away, I might have to add more acid malt to keep the pH ok. If the beer requires more hop flavor, I take away Calcium Chloride and add more to the Gypsum. If its a 100% malt forward style, I do the reverse.

The spreadsheet will tell you your mash pH with every adjustment, so keep your eye on that. I make sure my final minerals are in line, and just add or take away acid malt until my mash pH is in the range on that spreadsheet (5.4 - 5.6). Honestly, I don't measure my mash pH while I'm brewing but this is probably a good idea.

Usually, I end up adding about half my minerals to my mash, to acidify it, and about half in the boil, where they just affect the beers flavor.

Good luck!

  • Thanks, I will try this out soon and refrain from using tap water for the time being. Also, I'm curious - with many styles of sour beers out there does it really matter if the mash is overly acidic? I mostly see comments about alkalinity causing astringency by extracting tannins, and have yet to see anyone talking about acidity doing the same. Perhaps I haven't looked in the right places?
    – Daniel
    Jun 18, 2012 at 22:09
  • Without diving into the research, I'd do as normal a mash as possible on a sour, albeit I would mash warm to create some non-fermentables for the bugs to chew on later. I'm just thinking that given a sour's really long maturing process, I'd hate to discover 12 months in that something unusual I did in the mash was causing some weird flavor. And if low pH caused no problems at all, we'd probably all be dumping in handful of extra acid into each mash, so there's prob some specific problem with pH being too low.
    – GHP
    Jun 19, 2012 at 12:04
  • You want a normal mash process for sour beers. Its still about converting sugars. Souring is done in the fermentor. You can make small adjustments in recipe or mash routine to get the residual dextrins Graham mentions, but 95% of the mash process would still be the same sacch rest goals.
    – brewchez
    Jun 19, 2012 at 23:05
  • A batch with bottled spring water is a good idea to rule out tap water. But Seattle has pretty god water sources so I'd be surprised if that's the issue.
    – brewchez
    Jun 19, 2012 at 23:06

Someone gave me a tip when I started that I followed, and it might make a difference for you.

The grain bed is your best filter. Once you are done mashing you will sparge to separate the sugar from the grain. During this stage you want to make sure that the wort is running clear before you start collecting it. I use a pitcher to collect from the grain and I just pour it back over the grain-bed until it starts to be not-cloudy. It should be dark, but you want the fluid to not have any of the cloudy part that comes from the grain. This cloudy part is grain too and if it is boiled it can product excess tannin, which could create the flavors that you describe.

  • I was thinking this may be the culprit, but I'm not sure how to accomplish this without a mash tun. I've tried using the bottling bucket and just leaving the bag in, but either the wort never runs clear or it get clogged up and nothing comes out. Any tips on how to accomplish this without extra equipment to test and see if that's my issue?
    – Daniel
    Jun 18, 2012 at 2:07
  • 2
    You can try to make a false bottom out of one bucket inside another. I had a friend that tried this. You drill holes in the bottom of the bucket and put it inside the other bucket. You want to not use the bag, because you won't be able to form a proper grain bed when your grains are in a bag.
    – ChipJust
    Jun 18, 2012 at 2:13
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    Interesting. I will see what I can come up with, but I'm wondering how other brew-in-a-bag people do it. I see plenty of videos online where they just do BIAB in their pot, take out the grain and turn on the burners for the boil. If this were really my issue wouldn't that cause this flavor for those people?
    – Daniel
    Jun 18, 2012 at 2:18
  • 3
    Sorry, but Daniel is correct in his comment above. There is not need for a vorlauf when doing Brew In a Bag. Thousands of home-brewers are doing it now and astringency from tannins doesn't seem to be a common problem. Honestly, if boiling grains directly caused astringency, then every traditional German lager (which goes through a decoction) would taste like burnt chalk (shudder).
    – GHP
    Jun 18, 2012 at 12:12

I have this exact same problem and it started showing up when I went to all grain. Some of the BSG kits I've done use a steeping grain process where the grains are pre-milled and they all turned out great. My extract brews have also been great. In every case I've used the same water source (tap water)...

From the first all-grain batch to my latest they have a dank grainy or sour flavor which makes it basically un-drinkable. Exactly as you describe it.

A friend who knows a bit more about the all-grain process stopped by last week and watched how I was mashing and he also gave the tip of running out some wort until it goes semi-clear. Interestingly he also suggested it might be milling the grain too fine, allowing more tannins to come through. The two combined are likely my issue as his calculations had me at a 90% efficiency which I'm told is almost impossible for an amateur home brewer.

Anyway it would be nice to know if you're able to sort out the problem. I'll do the same and post back here soon.


Mash problem can involve water, to or not to vorlauf, etc., but it all comes down to the grain. I would point to the process of using a blender to grind the grain and suggest this is the culprit. BIAB is fine, but I got to say, brewing of any kind takes way too much time to cut corners. Get a grinder or grind everything at your local homebrew store, a buddy's, wherever. I think it is the use of your blender that is causing the problem.


I've had the same problem and figured out what caused the dark color and terrible flavour. I see your original post was years back but I hope this helps you and other brewers. I primarily brew IPAs and had the same problem. The beer would turn dark and develop a very bad flavor that's hard to describe after bottling.

(FYI If you bottle conditioned at constant colder temperatures this probably won't help...)

Well any time that happened I stored the bottles at room temperature where temps ranged from 65-75F. I brewed a couple batches recently and stored all bottles in my colder basement and all beer stored in the cool temperature has been fine with no unwanted changes in color and flavor.

I removed a couple bottles and exposed them to higher temps and.. you guessed it.. the beer turned dark and developed the unpleasant taste.

So try to keep all bottles in a cooler temp, id say around 40-50F. It doesn't solve the problem completely because there's obviously something in the beer causing the chemical reactions that causes the bad flavor, but storing at colder temps should help and not kick off those reactions.

I also lowered the temperature of the sparge water just in case I was extracting tannins, etc.

  • If it was tannins from the sparge surely it would taste bad before bottling but it tastes amazing at that point. Only goes bad in the bottle, the temperature idea sounds interesting.
    – malhal
    Jul 5, 2018 at 8:59

I had a similar issue with a recent beer also, I had put it down to Dimethyl Sulfides that I inadvertently generated trying to get a rolling boil going by leaving a lid cover on. This article provides some good info on this topic.


  • Can you add some more clarification? I'm not sure I see how DMS would result in the issue Daniel described. I don't see anything in the link you provided that seems reasonably close to the dark/burnt/astringent qualities described in the original post.
    – thesquaregroot
    Apr 28, 2017 at 14:55

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